The invention relates to a method for forming a gellified polyurethane layer on a surface, notably of a mould, by spraying a liquid reaction mixture comprising polyol and isocyanates and which has a viscosity between 20 and 2000 centipoises.
The invention relates more particularly to a method for forming, by spraying, an elastomer layer of polyurethane which is preferably stable to light and which serves in particular for aesthetical recovering, such as the internal recovering of a vehicle. For this case more particularly the technique of the so-called "airless two components systems without solvent means" is used.
Due to the relatively high viscosity of such a reaction mixture, the relatively important thickness of the polyurethane layer, to the fact that it is useful to apply on the surface within a single passage, and finally due to the necessity of a quick gellification of the polyurethane in order to avoid the running off of the reactive material on the surface of the mould under the influence of the gravitation force, the following has been established. If the known technique is applied, micro air-bubbles remain enclosed in the gellified polyurethane layer due to a heterogenity caused by the spraying of the mixture on the surface, irregularities arise in the density and other physical characteristics, such as the colour of the thus formed layer by the prior art method.